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Parasites in the Academy
JAMES R. JACOBS, MD, PHD
DIRECTOR, STUDENT HEALTH SERVICES
WILCE STUDENT HEALTH CENTER
OFFICE OF STUDENT LIFE
This slideset was originally presented on 30 May 2013 in
Boston at the Annual Meeting of the American College Health
Association. Copyright for all photographs remains with the
respective copyright holders.
Parasites in the Academy
1 Introduction and Pre-Test
2
3
4
5
6
Helminthic Parasites
Protozoal Parasites
Ectoparasites
Hints
Post-Test
Parasites in the Academy
• Conflict of interest
– The presenter has NO actual or potential conflict
of interest in relation to this educational activity
or presentation
– There is no financial or other sponsorship of
this presentation
Parasites in the Academy
• Disclaimers
– The presenter is not responsible for errors or
omissions or for any consequences from application of
the information in this presentation and makes to
warranty, expressed or implied, with respect to the
currency, accuracy, or completeness of these contents.
Application of this information in a particular clinical
situation remains the professional responsibility of the
practitioner.
– Implications and treatments may differ in pediatrics
and in pregnancy.
– Implications and treatment do differ in
immunocompromised persons.
Parasites in the Academy
• Off-label use of medications
– Off-label uses of drugs are included
– A best effort has been made to distinguish
between approved and off-label uses of
medications, but don’t rely on this presentation as
legal guidance!
• A few explicit photos
• Multiple references in the handout
Parasites in the Academy
Pre-Test
Parasites in the Academy
1. Oral ivermectin can be
used to treat scabies
and is FDA-approved
for this indication.
PRE-TEST
A. True
B. False
Parasites in the Academy
PRE-TEST
2. Tinidazole and
A. True
metronidazole both
B. False
carry a warning against
concomitant alcohol
consumption.
Parasites in the Academy
3. Three weeks ago this
student was walking
barefoot on a sandy
beach in a tropical
country. The most
likely diagnosis is:
PRE-TEST
A. Nodular scabies
B. Schistosomiasis
C. Cutaneous larva
migrans
D. Tungiasis
Parasites in the Academy
4. Two weeks ago this
student was doing
field research in Costa
Rica. Preferred initial
intervention is:
PRE-TEST
A. Petroleum jelly
B. Broad spectrum
antibiotics
C. Oral albendazole
D. Topical lindane
Parasites in the Academy
5. The parasite causing
strongyloidiasis lives
primarily in the small
intestine of its human
host but typically
enters the host
through the foot.
PRE-TEST
A. True
B. False
Parasites in the Academy
6. Oral metronidazole
remains the preferred
treatment for
giardiasis.
PRE-TEST
A. True
B. False
Parasites in the Academy
7. Pediculosis is caused
by:
PRE-TEST
A.
B.
C.
D.
Mites
Lice
Chiggers
Fleas
Parasites in the Academy
8. One day after
participating in an
outdoor service
project at his
southeastern college,
this student’s rash is
most likely caused by:
PRE-TEST
A.
B.
C.
D.
Chigger bites
Spider bites
Flea bites
Contact dermatitis
Parasites in the Academy
9. The appearance of this
itchy rash is classic for:
PRE-TEST
A.
B.
C.
D.
Chiggers
Pediculosis
Bedbugs
Scabies
Parasites in the Academy
10. This rash is described
as generalized, scaly,
red papules and
burrows, suggesting:
PRE-TEST
A.
B.
C.
D.
Chiggers
Pediculosis
Bedbugs
Scabies
Parasites in the Academy
1 Introduction
Parasites in the Academy
1 Introduction
Parasites
Ectoparasites
Protozoa
Helminths
Parasites in the Academy
1 Introduction
Organisms that grow,
feed, and are sheltered
on or in another
organism but contribute
nothing to host survival
Parasites
Ectoparasites
Protozoa
Helminths
Lives on the outer
surface of its host
Unicellular eukaryotic
organisms
Worm-like parasites
Parasites in the Academy
1 Introduction
Organisms that grow,
feed, and are sheltered
on or in another
organism but contribute
nothing to host survival
Parasites
Ectoparasites
Protozoa
Helminths
Lives on the outer
surface of its host
Unicellular eukaryotic
organisms
Worm-like parasites
Pediculosis
Scabies
Laelaps
Pyemotes
Myiasis
Cheyletiella
House mite
Avian mite
Demodex
Tungiasis
Bedbugs
Fleas
Chiggers
Malaria
Chagas disease
Giardia
Cryptosporidium
Entamoeba histolytica
Cyclospora cayetanensis
Microsporidiosis
Babesiosis
Leishmania
Trichomonas
Schistosomiasis
Clonorchiasis
Echinococcosis
Trichinosis
Ascariasis
Dracunculiasis
Onchocerciasis
Strongloidiasis
Cutaneous larva migrans
Visceral larva migrans
Parasites in the Academy
1 Introduction
Organisms that grow,
feed, and are sheltered
on or in another
organism but contribute
nothing to host survival
Parasites
E
X
A
M
P
L
E
S
Ectoparasites
Protozoa
Helminths
Lives on the outer
surface of its host
Unicellular eukaryotic
organisms
Worm-like parasites
Pediculosis
Scabies
Laelaps
Pyemotes
Myiasis
Cheyletiella
House mite
Avian mite
Demodex
Tungiasis
Bedbugs
Fleas
Chiggers
Malaria
Chagas disease
Giardia
Cryptosporidium
Entamoeba histolytica
Cyclospora cayetanensis
Microsporidiosis
Babesiosis
Leishmania
Trichomonas
Schistosomiasis
Clonorchiasis
Echinococcosis
Trichinosis
Ascariasis
Dracunculiasis
Onchocerciasis
Strongloidiasis
Cutaneous larva migrans
Visceral larva migrans
E
X
A
M
P
L
E
S
Parasites in the Academy
1 Introduction
Organisms that grow,
feed, and are sheltered
on or in another
organism but contribute
nothing to host survival
Parasites
E
X
A
M
P
L
E
S
Ectoparasites
Protozoa
Helminths
Lives on the outer
surface of its host
Unicellular eukaryotic
organisms
Worm-like parasites
Pediculosis  Bedbugs 
Fleas
Scabies 
Chiggers 
Laelaps
Pyemotes
Myiasis 
Cheyletiella
House mite
Avian mite
Demodex
Tungiasis
Malaria
Chagas disease 
Giardia 
Cryptosporidium 
Entamoeba histolytica
Cyclospora cayetanensis 
Microsporidiosis 
Babesiosis
Leishmania
Trichomonas 
Schistosomiasis 
Clonorchiasis
Echinococcosis 
Trichinosis
Ascariasis
Dracunculiasis
Onchocerciasis
Strongloidiasis 
Cutaneous larva migrans 
Visceral larva migrans
E
X
A
M
P
L
E
S
Parasites in the Academy
1 Introduction
• Approach
– What is the parasite?
– What is the disease?
– Doing something about it.
Parasites in the Academy
1 Introduction
Source: N Engl J Med 2013;368:1817-25
Parasites in the Academy
2 Helminthic Parasites
Parasites in the Academy
2 Helminthic Parasites
Strongyloidiasis
Echinococcosis
Schistosomiasis
Cutaneous larva migrans
Parasites in the Academy
2 Helminthic Parasites
Strongyloidiasis
Parasites in the Academy
2 Helminthic Parasites
What is the parasite?
Strongyloidiasis
• Strongyloides stercoralis
– Transmission occurs mainly in
tropical and subtropical
regions
– Current geographic
distribution is poorly defined
• Southeast Asia, Africa, Middle
East, Caribbean, tropical Brazil,
temperate Spain, Appalachia
• Very dependent on sewage
management
• Estimated 30–100 million people
are infected worldwide
Parasites in the Academy
2 Helminthic Parasites
What is the parasite? (continued)
Strongyloidiasis
• Strongyloides stercoralis
– Acquired through direct contact
with contaminated soil during
agricultural, domestic, and
recreational activities
Image: emedicine.com
Parasites in the Academy
2 Helminthic Parasites
What is the parasite? (continued)
Strongyloidiasis
• Strongyloides stercoralis
– Known for ability to persist and
replicate within a host for
decades while producing few if
any symptoms
– Without appropriate therapy, the
infection does not resolve and
may persist for life
– No evidence for human-tohuman transmission
• Organ transplantation?
Parasites in the Academy
2 Helminthic Parasites
Strongyloidiasis
Image: cdc.gov
What is the disease?
• Strongyloidiasis
– Immunocompetent host
• Many are asymptomatic
• Mild intermittent symptoms
– GI
» Watery diarrhea (can be
chronic), cramping
– Pulmonary
» Cough, wheeze, chronic
bronchitis
– Skin
» Larva currens - “creeping”
urticaria (photos) and pruritus
Image: accessmedicine.com
Parasites in the Academy
2 Helminthic Parasites
Strongyloidiasis
What is the disease? (continued)
• Strongyloidiasis
– Immunocompromised host
• Disseminated disease
• Life-threatening (50%)
• In US most deaths are
iatrogenic when an unknown
asymptomatic carrier is
treated with
immunosuppressants
Parasites in the Academy
2 Helminthic Parasites
Strongyloidiasis
What is the disease? (continued)
• Strongyloidiasis
– Be suspicious
•
•
•
•
Persistent watery diarrhea
History of foot wounds then GI
Diarrhea + Cough + Rash
Travel to endemic areas
– Eeven decades prior
– Diagnosis is not standardized
Image: cdc.gov
• Most frequent procedure entails
direct examination of stool
specimens
– Often does not yield positive results even when the
disease is present
Image: www.nhm.ac.uk
• Alternative tests (serology and
polymerase chain reaction) are
more efficient
Parasites in the Academy
2 Helminthic Parasites
Doing something about it.
Strongyloidiasis
Severity
Mild or asymptomatic disease
ivermectin 200 mcg/kg po times 1-2 days
Disseminated disease
Hospitalization/ ICU
Off
Label
Parasites in the Academy
2 Helminthic Parasites
Echinococcosis
Parasites in the Academy
2 Helminthic Parasites
What is the parasite?
• Echinococcus granulosus
Echinococcosis
Echinococcus granulosus
Source: cdc.gov
– 2-7 mm tapeworm
– Endemic to sheep-raising areas
worldwide
– Definitive hosts: dogs
– Human infection through fecal-oral
route
• Echinococcus multilocularis
– 1-4 mm tapeworm
– Central and Eastern Europe, Russia,
China, Alaska, others
– Definitive hosts: foxes, coyotes,
dogs
– Hunting, trapping, and contact with
dogs in endemic areas
Parasites in the Academy
2 Helminthic Parasites
What is the disease?
Echinococcosis
• Echinococcus granulosus
– Cystic echinococcosis
• aka, hydatid disease
• Cysts occur in liver, lung, or both
• Complication: cyst rupture
• Echinococcus multilocularis
– Alveolar echinococcosis
• Infection behaves as a slowgrowing malignant tumor, with
metastases
• Human cases are rare but are more
dangerous than cystic
echinococcosis
Parasites in the Academy
2 Helminthic Parasites
Doing something about it.
Echinococcosis
Treatment
Off
Label
Cystic echinococcosis
Percutaneous aspiration, plus
albendazole
Alveolar echinococcosis
Wide surgical resection, plus
albendazole for several years
•
Parasites in the Academy
2 Helminthic Parasites
Schistosomiasis
Parasites in the Academy
2 Helminthic Parasites
What is the parasite?
Schistosomiasis
• Trematodes or flukes of the
genus Schistosoma
• Schistosoma mansoni
– Middle East, Africa, South America
• S. haematobium
Image: bvgh.org
– Africa, Middle East
• S. japonicum
– Indonesia, China, Southeast Asia
• Others
• Usually associated with poor
sanitation
Parasites in the Academy
2 Helminthic Parasites
What is the parasite? (continued)
• Schistosoma
Schistosomiasis
– Infection occurs when skin comes
in contact with contaminated
freshwater in which certain types
of snails that carry the parasite are
living
• Typically when wading, swimming,
bathing, or washing.
– Over several weeks, the parasites
migrate through host tissue and
develop into adult worms inside
the blood vessels
– Once mature, the worms mate and
females produce eggs
• Some of these eggs travel to the
bladder or intestine and are passed
into the urine or stool
Parasites in the Academy
2 Helminthic Parasites
What is the disease?
Schistosomiasis
• Schistosomiasis
– Acute = Katayama fever
• 2-8 weeks after exposure
• Acute hypersensitivity reaction
• Fever, myalgia, lethargy, cough,
wheeze, dypsnea
Parasites in the Academy
2 Helminthic Parasites
Schistosomiasis
What is the disease? (continued)
• Schistosomiasis
– Chronic
• Symptoms arise from prolonged
granulomatous inflammatory
response to schistosome eggs
trapped in various host tissues
–
–
–
–
Noncirrhotic portal hypertension
Hydronephrosis
Renal failure
Liver and bladder cancer
Parasites in the Academy
2 Helminthic Parasites
Doing something about it.
Schistosomiasis
Infection
Praziquantel
Schistosoma mansoni

S. haematobium

S. japonicum

Katayma fever

Plus steroids
Off
Label
Parasites in the Academy
2 Helminthic Parasites
Cutaneous
larva migrans
Parasites in the Academy
2 Helminthic Parasites
Cutaneous
larva migrans
What is the parasite?
• Nematodes of the
hookworm family
– Most common: Ancylostoma
braziliense
Ancylostoma braziliense
Image: petmedmobile.com
Parasites in the Academy
2 Helminthic Parasites
Cutaneous
larva migrans
What is the parasite? (continued)
• Nematodes of the
hookworm family
– Human infestation occurs
after skin contact with soil or
objects contaminated with
feces from infected animals
– These larvae cannot penetrate
the basement membrane of
human skin
• Cannot complete lifecycle
• Thus, self-limiting disease
Parasites in the Academy
2 Helminthic Parasites
Cutaneous
larva migrans
What is the disease?
• Cutaneous larva migrans
– Larvae migrate in the
epidermis for several month
– Severe itching
– Sleep disturbance is common
– Secondary infection is
common
Source: Am Fam Physician 81(2):203, 2010
Parasites in the Academy
2 Helminthic Parasites
Cutaneous
larva migrans
What is the disease?
• Cutaneous larva migrans
– Has been reported as the
most common skin disease in
returning travelers
Source: emedicine.com
Parasites in the Academy
2 Helminthic Parasites
Doing something about it.
Cutaneous
larva migrans
Option
ivermectin 200 mcg/kg single dose
Offlabel
•
albendazole 400 mg po bid x 3-7 days
• Ultimately self-limiting, but symptoms may
persist for months if not treated
• Pruritis typically resolves within 48 hours
– Skin lesions within a week
• Consider antibiotics for secondary bacterial
infections
Parasites in the Academy
3 Protozoal Parasites
Parasites in the Academy
3 Protozoal Parasites
Chagas disease
Giardiasis
Cryptosporidiosis
Cyclosporiasis
Microsporidiosis
Amebiasis
Trichomonas
Protozoan Infections of
the Gastrointestinal Tract
Parasites in the Academy
3 Protozoal Parasites
Chagas disease
Parasites in the Academy
3 Protozoal Parasites
What is the parasite?
Chagas disease
• Trypanosoma cruzi
– Parasite is restricted to Central
and South America, Mexico and
southern US
– Transmission
• Feces of certain bloodsucking
triatomine (Reduviidae family)
bugs
Triatomine bug
Image: news.co.cr
– Via the bug bite or into another
break in the skin
• Possible: uncooked food
• Rarely: blood transfusion,
transplants, mother-to-fetus, or
laboratory accident
Parasites in the Academy
3 Protozoal Parasites
What is the disease?
Chagas disease
• Chagas disease
– aka, American trypanosomiasis
– Has been found in preColumbian Andean mummies
from 9000 years ago
– Major public health challenge in
Latin America
– Now has spread to other
continents
• Prevalence in US has increased
substantially in past 20 years
• Immigration status keeps some in
US from seeking medical attention
Parasites in the Academy
3 Protozoal Parasites
What is the disease? (continued)
Chagas disease
• Chagas disease (continued)
– WHO estimates
• 7.7 to 10 million people chronically
infected
• 10,000 to 14,000 deaths per year
Parasites in the Academy
3 Protozoal Parasites
What is the disease? (continued)
Chagas disease
• Chagas disease (continued)
– Acute phase
• Most are asymptomatic, or
• Prolonged fever, malaise enlargement
of the liver, spleen, and lymph nodes,
and subcutaneous edema
– ECG might show sinus tachycardia, firstdegree AV-block, low QRS voltage, or
primary T-wave changes
– Chest radiograph might show variable
degrees of cardiomegaly
Parasites in the Academy
3 Protozoal Parasites
What is the disease? (continued)
Chagas disease
• Chagas disease (continued)
– Chronic phase
• Begins 2 to 3 months after initial
infection
• Indeterminate form
– 60% to 70% of patients
– No clinical symptoms
• Determinate form
– 30%–40% of patients
– Cardiac, digestive (mainly megaesophagus
and megacolon), or cardiodigestive forms
– Usually 10 to 30 years after initial infection
• Reactivation of Chagas disease can also
occur in chronically infected patients
who become immunologically
compromised
Parasites in the Academy
3 Protozoal Parasites
What is the disease? (continued)
Chagas disease
Chagas similar to HIV
Chagas different than HIV
Acute and chronic phases
Parasite
Can be infected for years
without knowing it
Most transmission occurs
through bug bite or
contaminated food
Transmission though
transfusions and in utero
Primarily affects heart
and GI tract
Disproportionate burden
on the poor
Most people never
develop chronic
symptoms
Prolonged treatment,
ideally started during
acute phase
Prevalence limited
primarily to habitat of
certain bugs
Parasites in the Academy
3 Protozoal Parasites
Doing something about it.
Chagas disease
Referral
Prevention: Advise travelers to avoid dirtfloored jungle huts near a beach
Parasites in the Academy
3 Protozoal Parasites
Giardiasis
Cryptosporidiosis
Cyclosporiasis
Microsporidiosis
Amebiasis
Protozoan Infections of
the Gastrointestinal Tract
Parasites in the Academy
3 Protozoal Parasites
What is the parasite?
Giardiasis
Cryptosporidiosis
Cyclosporiasis
Microsporidiosis
Amebiasis
Protozoan Infections of
the Gastrointestinal Tract
• Giardia lamblia
• Worldwide
• Infecting dose as low as 10 cysts
• Pool chlorination does not
kill
• Transmission: fecal-oral
• Cryptosporidium hominis
• Cryptosporidium parvum
• Others
• Temperate and tropical regions
• Transmission: fecal -oral
Parasites in the Academy
3 Protozoal Parasites
What is the parasite? (continued)
Giardiasis
Cryptosporidiosis
Cyclosporiasis
Microsporidiosis
Amebiasis
Protozoan Infections of
the Gastrointestinal Tract
• Cyclospora cayetanensis
• Peru and Nepal
• Transmisstion: infected
uncooked foods, such as basil,
raspberries and snow peas
• Encephalitozoon intestinalis
• Enterocytozoon bieneusi
• 1200 others
• Worldwide
• Transmisson:
Parasites in the Academy
3 Protozoal Parasites
What is the parasite? (continued)
Giardiasis
Cryptosporidiosis
Cyclosporiasis
Microsporidiosis
Amebiasis
Protozoan Infections of
the Gastrointestinal Tract
• Entamoeba histolytica
• Mostly Far East
• Transmission: fecal-oral
Parasites in the Academy
3 Protozoal Parasites
What is the disease?
Giardiasis
Cryptosporidiosis
Cyclosporiasis
Microsporidiosis
Amebiasis
Protozoan Infections of
the Gastrointestinal Tract
• Giardiasis
– Incubation period 8 days
– Sudden onset watery diarrhea
with yellow foul-smelling
stools and flatus
– Abdominal distension
– Anorexia
– Malabsorption can occur
– Fecal microscopy ± antigen
detection
Parasites in the Academy
3 Protozoal Parasites
Giardiasis
Cryptosporidiosis
Cyclosporiasis
Microsporidiosis
Amebiasis
Protozoan Infections of
the Gastrointestinal Tract
What is the disease? (continued)
• Cryptosporidiosis
– Small bowel infection
– Mild, watery diarrhea lasting
1-40 days
– Systemic upset is uncommon
Parasites in the Academy
3 Protozoal Parasites
Giardiasis
Cryptosporidiosis
Cyclosporiasis
Microsporidiosis
Amebiasis
Protozoan Infections of
the Gastrointestinal Tract
What is the disease? (continued)
• Cyclosporiasis
– Incubation period 12 days
– Acute watery diarrhea
– Mild systemic upset
Parasites in the Academy
3 Protozoal Parasites
Giardiasis
Cryptosporidiosis
Cyclosporiasis
Microsporidiosis
Amebiasis
Protozoan Infections of
the Gastrointestinal Tract
What is the disease? (continued)
• Microsporidiosis
– Worldwide
– Most immunocompetent
hosts are asymptomatic for
years
– Most interest resolves around
effects on hosts with immune
compromise
• Diarrhea and malpabsoprtion
Parasites in the Academy
3 Protozoal Parasites
Giardiasis
Cryptosporidiosis
Cyclosporiasis
Microsporidiosis
Amebiasis
Protozoan Infections of
the Gastrointestinal Tract
What is the disease? (continued)
• Amebiasis
– Amebic dysentary
• Large bowel-type diarrhea
• Bloody stools
• Mild to life-threatening
Parasites in the Academy
3 Protozoal Parasites
Giardiasis
Cryptosporidiosis
Cyclosporiasis
Microsporidiosis
Amebiasis
Protozoan Infections of
the Gastrointestinal Tract
What is the disease? (continued)
• Common features
– Diarrhea
– Worse in HIV and other
immune compromise
– Mostly oral-fecal transmission
• Potential for sexual transmission
Parasites in the Academy
3 Protozoal Parasites
Doing something about it.
Giardiasis
Cryptosporidiosis
Cyclosporiasis
Microsporidiosis
Amebiasis
Protozoan Infections of
the Gastrointestinal Tract
Disease
Treatment for uncomplicated cases in
immunocompetent patient
Giard
metronidazole 250 mg po tid x 10 d, or
metronidazole 2 g po daily for 3 d, or
tinidazole 2 g po single dose
Crypto
nitazoxanide 500 mg po bid x 3 days
Cyclo
TMP-SMZ DS 1 po bid for 7 days
Micro
albendazole 400 mg po bid x 21 d
Ameb
metronidazole 750 mg po bid x 5-10 d, or
Tinidazole 2 g daily for 3 d
Parasites in the Academy
3 Protozoal Parasites
Trichomonas
Parasites in the Academy
3 Protozoal Parasites
Trichomonas
Source: pathobio.sdu.edu.cn
• OSOM…Affirm VP III…APTIMA…
PRC…none are approved for use
with males
• Males: consider in prostatitis,
epididymitis, and balanitis, in
addition to urethritis
• Has not been isolated form oral
sites
• Very low rectal prevalence in MSM
• Oral metronidazole remains drug of
choice
– Tinidazole (2 g po) is alternative
Parasites in the Academy
4 Ectoparasites
Parasites in the Academy
4 Ectoparasites
Pediculosis
Scabies
Myiasis
Tungiasis
Bed bugs
Chiggers
Parasites in the Academy
4 Ectoparasites
Pediculosis
Parasites in the Academy
4 Ectoparasites
Pediculosis
What is the parasite?
• Lice
– Pediculosis humanus var.
capitas
• 2-3.3 mm
• Most transmission is probably
head-to-head
Head louse (original magnification x 40)
Int J Derm 2012, 51, 131–141
– Louse can survive off of host for up to
55 hours
• Lays eggs (nits) close to scalp
– Hatch within 12 days
Parasites in the Academy
4 Ectoparasites
Pediculosis
What is the parasite? (continued)
• Lice
– Pediculosis humanus var.
corporis
• Live in the seams of clothing
and attach to skin only to feed
Parasites in the Academy
4 Ectoparasites
Pediculosis
What is the parasite? (continued)
• Lice
– Phthirus pubis
Source: cdc.gov
• 1.1-1.8 mm
• Typically found attached to hair
in the pubic area
• Sometimes are found on coarse
hair elsewhere on the body
– Eyebrows, eyelashes, beard,
mustache, chest, axillae, etc.
• Usually spread through sexual
contact
Parasites in the Academy
4 Ectoparasites
What is the disease?
Pediculosis
• Pediculosis capitis
– Pediculosis humanus var. capitas
– “Head lice”
• Live lice (tiny black dots) and nits
• Infestation can cause pruritis and rash
– Red papules, typically found in the
posterior scalp and neck and behind ears
– Possible cervical adenopathy
• Often asymptomatic
• Chronic infestation has been
associated with superinfection with
MRSA or nephritogenic strains of strep
Parasites in the Academy
4 Ectoparasites
Pediculosis
What is the disease? (continued)
• Pediculosis corporis
– Pediculosis humanus var.
corporis
– “Body lice”
• Characteristic skin lesions
include erythematous macules
and wheals
– Most common on the shoulders,
buttocks and abdomen
– Furunculosis is an occasional
complication
Parasites in the Academy
4 Ectoparasites
Pediculosis
What is the disease? (continued)
• Pediculosis pubis
– Phthirus pubis
– Pubic lice = “crabs”
• Infestation tends to be limited
to pubic hair
– Occasionally affects axillae, eyelashes,
or other hairy parts
• Examination reveals lice
attached to the skin and lice
eggs attached to the hair shafts
Parasites in the Academy
4 Ectoparasites
Doing something about it.
Pediculosis
Head Lice
Chemical
Pyrethrin 0.3% shampoo (e.g., RID), apply for 10
min and rinse, repeat in 7-10 d, or
Permethrin 1% rinse (e.g., Nix), apply for 10 min,
repeat in 7-10 d, or
Malathion 0.5% lotion (e.g., Ovide), apply to dry
hair for 8-12 hr daily for 1 wk, or
Spinosad – very expensive, or
Ivermectin 200 mcg/kg po, repeat in 7-10 d, or
Others
Environmental and Physical
Nit combing; dry bedding and clothes at 60 C for
10 min; boil hair combs etc; vacuum furniture;
bag non-launderables for 3 d
Off
Label
•
Parasites in the Academy
4 Ectoparasites
Doing something about it.
Pediculosis
Body Lice
Patient
Antiparasitic medications generally not required
Clothing
Discard, or
Treat with 1% malathion powder or 5% permethrin
powder (pesticides)
Parasites in the Academy
4 Ectoparasites
Doing something about it.
Pediculosis
Pubic Lice
Off
Label
Pubic and Other Coarse Hair
Permethrins or malathion, same as for head
lice
Eyelashes and Eyebrows
Fine comb is preferred
If additional treatment is needed, careful
application of ophthalmic-grade petrolatum
ointment (Rx) to the eyelid margins 2-4
times a day for 10 days is usually effective;
avoid regular petrolatum
Also, treatment of intimate partners from the past
month, clothing, bedding, etc
•
Parasites in the Academy
4 Ectoparasites
Scabies
Parasites in the Academy
4 Ectoparasites
What is the parasite?
Scabies
• Sarcoptes scabei var. hominis
– Mite (arthropod)
– Obligate parasite
• Completes its entire life cycle on humans
– Females 0.3-0.4 mm
– Feed on human skin
Scabies mite
Int J Derm 2012, 51, 131–141
• Often burrow into the skin while doing
so
• Adult female lays her eggs inside the
burrows
– Not able to fly or jump
• Transmission predominantly through
direct skin-to-skin contact
• Able to live on bedding, clothes, or other
surfaces at room temperature for < 48
hours
Scabies mite
dimensionsinfo.com/how-big-are-scabies-mites/
Parasites in the Academy
4 Ectoparasites
What is the disease?
Scabies
• Classic scabies
• Crusted scabies
• Nodular scabies
Parasites in the Academy
4 Ectoparasites
What is the disease? (continued)
Scabies
• Classic scabies
– Intensely pruritic and highly
contagious skin infestation
• Described by Aristotle
• First human disease recognized to be
caused by a specific pathogen (1687)
– Affects all socioeconomic status
and ethnic groups
– Estimated 300 million cases per
year worldwide
Parasites in the Academy
4 Ectoparasites
What is the disease? (continued)
Scabies
• Classic scabies (continued)
– Typically only 5-15 mites
– Little evidence of infection exists
during the first month
– After 4 weeks and with subsequent
infections, a delayed-type IV
hypersensitivity reaction to the
mites, eggs, feces occurs
• In re-infestation, the sensitized
individual may develop a rapid
reaction (within hours)
– The resultant skin eruption, and its
associated intense pruritus, is the
hallmark of classic scabies
Parasites in the Academy
4 Ectoparasites
What is the disease? (continued)
Scabies
• Classic scabies (continued)
– The resultant skin eruption, and its
associated intense pruritus, is the
hallmark of classic scabies
• Burrows may be seen as an irregular
zigzag line in the stratum corneum
• Secondary lesions represent
immunologic reactions and usually
appear as small erythematous papules
and vesicles
• Pruritis is often worse in the evening
• Areas most commonly involved are
the interdigital web spaces of the
hands, the flexor surfaces of the
wrists, the periumbilical skin, and
genitalia
Source: picturesofscabies.org
Parasites in the Academy
4 Ectoparasites
What is the disease? (continued)
Scabies
• Classic scabies (continued)
– Diagnosis
• Usually based on history and
skin findings
• Microscopy of burrow scraping
• Skin biopsy
Parasites in the Academy
4 Ectoparasites
What is the disease? (continued)
Scabies
Source: dermatology.cdlib.org
Source: dermatology.cdlib.org
• Crusted scabies
– aka, Norwegian scabies
– Distinctive and highly contagious
– Hundreds to millions of mites infest
the host individual, who is usually
immunocompromised, elderly, or
physically or mentally disabled and
impaired
– Easily confused with severe
dermatitis or psoriasis because
widespread, crusted lesions appear
with thick, hyperkeratotic scales
over the elbows, knees, palms, and
soles
Parasites in the Academy
4 Ectoparasites
What is the disease? (continued)
Scabies
Scabietic nodules
Indian Dermatol Online J. 2013; 4(1): 52–53
• Nodular scabies
– Pruritic, persistent nodules for
months even after specific
treatment of scabies
– Probably represents the
hypersensitivity reaction to
retained mite parts or antigens
– Genital skin and scrotal skin are
the commonest sites for such
lesions.
Parasites in the Academy
4 Ectoparasites
Doing something about it.
Scabies
Classic scabies
permethrin cream 5% (apply to all skin
from chin down, to include under
nails, leave on 8-14 hrs, repeat in 12wks), or
ivermectin 200 mcg/kg po (± repeat in
2 weeks)
Offlabel
•
Postscabies itch can persist for months
Consider re-check at 4 weeks
Important to trim nails and to reapply cream to
hands and under finger nails after washing
hands during treatment period
Parasites in the Academy
4 Ectoparasites
Doing something about it.
Scabies
Crusted scabies
permethrin cream 5% daily for 7 days,
then twice weekly until cured, plus
ivermectin 200 mcg/kg po on days 1, 2, 8,
9, 15, 22, 29
Address underlying medical issues
Offlabel
•
•
Parasites in the Academy
4 Ectoparasites
Doing something about it.
Scabies
Nodular scabies
intralesional steroids
topical steroids
pimecrolimus (Elidel)
tacrolimus (Protopic)
Offlabel
•
•
Parasites in the Academy
4 Ectoparasites
Furuncular
Myiasis
Parasites in the Academy
4 Ectoparasites
Furuncular
Myiasis
What is the parasite?
• Larvae of Dermatobia hominis
– Human “botfly”
– Endemic to tropical Mexico, South
America, Central America, Trinidad
• Cordylobia anthropophaga
– “Tumbu fly”
– Endemic to sub-Saharan Africa
Source: flickr.com/photos/diegoalmeida
Myiasis: infestation of maggots
• Others
Parasites in the Academy
4 Ectoparasites
Furuncular
Myiasis
What is the parasite? (continued)
• Mode of transmission
– Eggs from an adult female become
attached to the abdomen of a
blood-sucking arthropod
• Typically a mosquito
Source: flickr.com/photos/rainforests
Source: mybotfly.com/stories.htm
– While the mosquito is feeding, the
victim’s body heat causes the egg
to hatch and the larva falls onto the
victim’s skin
– The larva enters the skin through
the bite wound or through some
other small break in the skin
– The larva grows to 1.5-2 cm and
emerges from the host in 6-7
weeks
Parasites in the Academy
4 Ectoparasites
Furuncular
Myiasis
What is the disease?
• Furuncular myiasis
– aka, warble
– Usually presents as a slowly
growing nodule that resembles a
pustule or papule with a central
punctum
– Punctum
• May exude serosanguinous or
purulent fluid
• Posterior part of the larva can
sometimes be visualized
Botfly myiasis
Source: emedicine.com
– Pruritis, pain, movement sensation
– Disease from tumbu fly is generally
much more extensive than from
botfly
Parasites in the Academy
4 Ectoparasites
Parasites in the Academy
4 Ectoparasites
Furuncular
Myiasis
Doing something about it.
Method
Recommendation
Suffocation
Place petroleum jelly, tape, bacon, or
similar over the punctum – larva will
back out of the hole as breathing
becomes difficult, plus
Topical antibiotic
Extraction
Simple forceps or formal excision –
take care not to damage the larva in
the process, plus
Topical antibiotic
Remain watchful for secondary bacterial infection.
Parasites in the Academy
4 Ectoparasites
Tungiasis
Parasites in the Academy
4 Ectoparasites
What is the parasite?
Tungiasis
Source: dimusbahia.files.wordpress.com
• Tunga penetrans or related species
– Burrowing flea
– Smallest known flea (1 mm)
– Warm, dry soil and sand of beaches,
stables, and stock farms
– West Indies, Caribbean, Central
America, Africa, India, Pakistan, and
South America
– Many common names
• chigger flea, sand flea, chigoe, jigger,
nigua, pigue, or le bicho de pe
– Flea requires a warm-blooded host
• Humans, pigs, dogs, cats, cattle, sheep,
horses, mules, rats, mice, and other wild
animals
Parasites in the Academy
4 Ectoparasites
What is the disease?
Tungiasis
Source: visualphotos.com
Source: visualphotos.com
• Tungiasis
– aka, nigua, pio, bicho de pie, and
pique
– Flea invades unprotected skin
• Most common site of involvement is
the feet (interdigital skin and
subungual area)
• Can occur on any area of the body to
which the flea has access
Parasites in the Academy
4 Ectoparasites
What is the disease? (continued)
Tungiasis
• Tungiasis
– Pain or itching and papular or
nodular eruptions
• typically forms a punctum or an
ulceration
• Often described as a white patch with
a black dot
Source: J Am Acad Dermatol 2012;67:331.e13
– Over ≈2 weeks the flea feeds,
becomes engorged, and expels
eggs
• Afterwards, the flea dies and is slowly
sloughed by the host
– Uncomplicated infestation results
in pain, swelling, tenderness
• Potential complications include
secondary infections and tetanus
Source: emedicine.com
Parasites in the Academy
4 Ectoparasites
Doing something about it.
Tungiasis
Goal
Recommendation
Prevention
Travelers to affected countries should
be advised to wear shoes (not
sandals) when walking along sandy
areas in affected regions and to
refrain from sitting or lying in the
sand
Insect repellant Zanzarin
Treatment
Surgical excision plus topical antibiotic
Secondary
infection
Tetanus prophylaxis
Antibiotics as needed
Parasites in the Academy
4 Ectoparasites
Bed bugs
Parasites in the Academy
4 Ectoparasites
What is the parasite?
Bed bugs
• Cimex lectularius
– Worldwide
• Cimex hemipterus
•
•
•
•
Cimex lectularius
Source: cirbus.com
– Tropical
5-8 mm, reddish-brown insect
Wingless
Avoid light
Relies mostly on humans for
survival
– Attracted by warmth and carbon
dioxide
– Feed on blood for a few min at a time
– Mostly during the night in the dark
• Speculated to be a vector for other
pathogens but vector competence
not proven
Parasites in the Academy
4 Ectoparasites
What is the disease?
Bed bugs
• Bed bug bites
• Bed bug infestation
Parasites in the Academy
4 Ectoparasites
What is the disease? (continued)
Bed bugs
Source: bedbugle.com
• Bed bug bites
– Can be asymptomatic
– Papular urticaria, mascules, bullous
lesions
• Reaction to bug’s saliva
• Often in clusters and lines
• Reactions develop over minutes to
days
• Decreased latency on repeated
exposure
– Difficult to distinguish from bite of
fleas, spiders, and other insects
Parasites in the Academy
4 Ectoparasites
Bed Bug Bites
Parasites in the Academy
4 Ectoparasites
What is the disease? (continued)
Bed bugs
Source: orovidermagazine.com
Source: Clin Microbiol Rev 2012;25:164-192
• Bed bug infestation
– Fundamentally an environmental
problem
– Requires an experienced
exterminator
Parasites in the Academy
4 Ectoparasites
Doing something about it.
Bed bugs
Bed bug bites
Pruritis – antihistamines and topical steroids
Secondary infection (rare) – antibiotics as needed
Assess psychological distress
Bed bug infestation
Professional disinfestation
Environmental controls
Parasites in the Academy
4 Ectoparasites
Chiggers
Parasites in the Academy
4 Ectoparasites
What is the parasite?
Chiggers
Chigger
emedicine.com
• Eutrombicula alfreddugesi
–
–
–
–
Most common species in the United States
Trombiculid mite
Adult mite is not a human parasite
Larval form
• Adult female lays eggs in the soil
• Larval form hatches after 1-2 weeks
– Known as a chigger, red bug, or harvest mite
– Lives in the grass, soil, and weeds and requires a
meal from a vertebrate host to mature
• Does not feed on blood
– Rather, it crawls onto the host, anchors itself to
the skin, injects proteolytic enzymes, and ingests
the degraded tissue
Chigger
Cutis 2006;77(6):350
• May remain attached to the host for 3-4 days,
then drops off into the soil to complete its
maturation
Parasites in the Academy
4 Ectoparasites
What is the parasite?
Chiggers
(continued)
• Eutrombicula alfreddugesi
– Worldwide distribution (many species)
– In US
• Particularly abundant in southeastern and south
central states
• Bites most common late summer and early
autumn
Parasites in the Academy
4 Ectoparasites
What is the disease?
Chiggers
• Chigger bites
– Painless
– Produce a 2- to 3-mm pale macule
– Initially, the larva may still be attached,
appearing as a 1-mm red dot in the center of a
macule
– Over time, the lesions enlarge and become
erythematous and intensely pruritic grouped
papules or papulovesicles
• Lesions typically are found on the ankles and
lower extremities but also appear on moist
areas of the body (eg, axillae, genitalia, popliteal
and antecubital fossae)
Chiggers bites on an ankle
Cutis 2006;77(6):351
– Pruritus starts within a few hours of a bite and
ceases in a few days
– Lesions heal in 1 to 2 weeks
Parasites in the Academy
4 Ectoparasites
What is the disease? (continued)
Chiggers
• In the Far East, chiggers can be a
vector for transmission of Rickettsia
tsutsugamushi, the infectious agent of
scrub typhus
Parasites in the Academy
4 Ectoparasites
Doing something about it.
Chiggers
Goal
Strategy
Prevention
Avoidance
Protective clothing
Insect repellents
Reduce
Topical steroids
pruritis
Topical anesthetics
(all anecdotal) Topical counterirritants
Ex: deodorant sticks
containing propylene glycol
Secondary
infection
Off
Label
•
Treat as needed
Note: by the time the itching starts the mite
has long since left the skin.
Parasites in the Academy
5 Hints
Parasites in the Academy
5 Hints
• Pruritus
– Oral medications
• Antihistamines
– Efficacy data are limited, but inexpensive and generally safe
– No direct effect on pruritus except in urticaria
– Typically diphenhydramine (OTC) or hydroxyzine (Rx)
– Topical medications
• Topical corticosteroids
– Not indicated for pruritus without evidence of skin inflammation
– Typically hydrocortisone (OTC) or triamcinalone (Rx)
• Consider topical capsaicin* lotion (OTC) and topical doxepin (Rx)
– Many additional options
– Most important: remove inciting cause
* = off-label
Parasites in the Academy
5 Hints
• tinidazole (Tindamax)
– Approved indications: amebiasis, bacterial vaginosis,
giardiasis, trichomonas
– Available generic and branded
– Available as 250 and 500 mg tablet
– Take with food
– Chemical structure similar to metronidazole
• Potential for disulfiram-type reaction in some patients
• Alcoholic beverages should not be consumed for at least one day
after completion of metronidazole therapy and for 3 days after
completion of tinidazole therapy.
Parasites in the Academy
5 Hints
• ivermectin (Stromectol)
–
–
–
–
–
Approved uses: onchocerciasis & intestinal strongyloidiasis
Off-label uses: many
Available as 3 mg tablet
Typical dose = 200 mcg/kg
Example for 175 lb patient
• 200 mcg/kg x 1 mg/1000 mcg x 175 lb x 1 kg/2.2 lb = 15.9 mg
• 15.9 mg 3 mg tab ≈ 5 tablets
ivermectin
dose
200 mcg/kg
≈ # ivermectin tablets (3 mg) based on weight (lbs)
140
160
180
200
220
300
4
5
5
6
7
9
Parasites in the Academy
5 Hints
• permethrins
– 1% lotion/cream rinse (OTC: Nix, others)
• Approved use: head lice
– 1% liquid/shampoo (OTC: RID, others)
• Approved use: head lice
– 5% cream (Rx: Elimite, Acticin, generics)
• Approved use: scabies
Parasites in the Academy
5 Hints
• Diarrhea
–
–
–
–
Stool Culture
Stool for Ova & Parasites
Basic vs. comprehensive
Specific serology
• Skin scrapings
– KOH prep vs. scabies prep vs. other
Parasites in the Academy
5 Hints
• Unexplained jaundice in a traveler
– Consider protozoal and helminthic infections
• Unexplained eosinophilia in a traveler
– Consider helminthic infection
• Papular urticaria
– Consider ectoparasites
6 Parasites in the Academy
Post-Test
6 Parasites in the Academy
1. Oral ivermectin can be
used to treat scabies
and is FDA-approved
for this indication.
POST-TEST
A. True
B. False
6 Parasites in the Academy
1. Oral ivermectin can be
used to treat scabies
and is FDA-approved
for this indication.
POST-TEST
A. True
B. False
6 Parasites in the Academy
POST-TEST
2. Tinidazole and
A. True
metronidazole both
B. False
carry a warning against
concomitant alcohol
consumption.
6 Parasites in the Academy
POST-TEST
2. Tinidazole and
A. True
metronidazole both
B. False
carry a warning against
concomitant alcohol
consumption.
6 Parasites in the Academy
3. Three weeks ago this
student was walking
barefoot on a sandy
beach in a tropical
country. The most
likely diagnosis is:
POST-TEST
A. Nodular scabies
B. Schistosomiasis
C. Cutaneous larva
migrans
D. Tungiasis
6 Parasites in the Academy
3. Three weeks ago this
student was walking
barefoot on a sandy
beach in a tropical
country. The most
likely diagnosis is:
POST-TEST
A. Nodular scabies
B. Schistosomiasis
C. Cutaneous larva
migrans
D. Tungiasis
6 Parasites in the Academy
4. Two weeks ago this
student was doing
field research in Costa
Rica. Preferred initial
intervention is:
POST-TEST
A. Petroleum jelly
B. Broad spectrum
antibiotics
C. Oral albendazole
D. Topical lindane
6 Parasites in the Academy
4. Two weeks ago this
student was doing
field research in Costa
Rica. Preferred initial
intervention is:
POST-TEST
A. Petroleum jelly
B. Broad spectrum
antibiotics
C. Oral albendazole
D. Topical lindane
6 Parasites in the Academy
5. The parasite causing
strongyloidiasis lives
primarily in the small
intestine of its human
host but typically
enters the host
through the foot.
POST-TEST
A. True
B. False
6 Parasites in the Academy
5. The parasite causing
strongyloidiasis lives
primarily in the small
intestine of its human
host but typically
enters the host
through the foot.
POST-TEST
A. True
B. False
6 Parasites in the Academy
6. Oral metronidazole
remains the preferred
treatment for
giardiasis.
POST-TEST
A. True
B. False
6 Parasites in the Academy
6. Oral metronidazole
remains the preferred
treatment for
giardiasis.
POST-TEST
A. True
B. False
6 Parasites in the Academy
7. Pediculosis is caused
by:
POST-TEST
A.
B.
C.
D.
Mites
Lice
Chiggers
Fleas
6 Parasites in the Academy
7. Pediculosis is caused
by:
POST-TEST
A.
B.
C.
D.
Mites
Lice
Chiggers
Fleas
6 Parasites in the Academy
8. One day after
participating in an
outdoor service
project at his
southeastern college,
this student’s rash is
most likely caused by:
POST-TEST
A.
B.
C.
D.
Chigger bites
Spider bites
Flea bites
Contact dermatitis
6 Parasites in the Academy
8. One day after
participating in an
outdoor service
project at his
southeastern college,
this student’s rash is
most likely caused by:
POST-TEST
A.
B.
C.
D.
Chigger bites
Spider bites
Flea bites
Contact dermatitis
6 Parasites in the Academy
9. The appearance of this
itchy rash is classic for:
POST-TEST
A.
B.
C.
D.
Chiggers
Pediculosis
Bedbugs
Scabies
6 Parasites in the Academy
9. The appearance of this
itchy rash is classic for:
POST-TEST
A.
B.
C.
D.
Chiggers
Pediculosis
Bedbugs
Scabies
6 Parasites in the Academy
10. This rash is described
as generalized, scaly,
red papules and
burrows, suggesting:
POST-TEST
A.
B.
C.
D.
Chiggers
Pediculosis
Bedbugs
Scabies
6 Parasites in the Academy
10. This rash is described
as generalized, scaly,
red papules and
burrows, suggesting:
POST-TEST
A.
B.
C.
D.
Chiggers
Pediculosis
Bedbugs
Scabies